Did you follow the suggestion that @paddywag mentioned in the article you attached? Also, we'd like you to try to log in by using your Facebook email address as username and password. Make sure not to use the Log in with Facebook option.
If you're still unable to access, go to your Facebook profile > Settings > Apps, and remove Spotify from the list. Once you've done that, you should be able to log in with the blue button to log in with Facebook.
I tried using the "Log in with Facebook" option today and it was successful. I didn't get to try your suggestions since the issue appears to already have been fixed. Can't reproduce the problem anymore.
Hey @camelmeal!
We're glad to hear it's working now, we had a hiccup that could've caused this, but it was promptly fixed.
If anything else comes up, don't hesitate to open a new thread.
All the best.